The present invention relates to a process for painting polyolefinic resin components.
Hitherto, metal was used in addition to glass for trim parts of automobiles. Recently, resin components were often used for bumpers, door mirror covers, moule, spoilers and the like. As such resin components, polyolefinic resin is often used because it has better cost performance than that of urethane resin.
The painting of the surface of these polyolefinic resin components has many restrictions different from the painting of metal. Namely, 1. since the polyolefinic resin has a small polarity and paints or painting films are difficult to adhere on the surface, only a specified paint can be used. Further, 2. upon heating and drying, the temperature should he below 120.degree. C. In spite of these restrictions, upon painting and coating, the same ability of adherence, visual appearance, weather resistance, chemical resistance, solvent resistance and the like is required as that of the surface of automobiles.
To improve the adherence of paints on the surface of polyolefinic resin components, the surface is pretreated by flame treatment, corona discharge, plasma treatment, chrome sulfate treatment or the like, and then the surface is paintea with a facing material. However, these methods do not always give sufficient adherence because of the complex form.
As a different method, the surface of polyolefinic resin components is washed with a solvent such as trichloroethane, the surface is painted with an exclusive primer having good adherence, and a facing material is used. However, there are problems that many steps are used in this method. Since the primer is expensive, the total cost increases.
To improve the technique, resin or paints having good adherence to the surface of polyolefinic resin are disclosed as follows.
a. In Japanese Patent Laid-Open Publication Number 57-200438, a mixture of chlorinated polyolefinic resin and acrylic resin.
b. In Japanese Patent Laid-Open Publication Numbers 59-27968 and 62-149734, a resin combining a copolymer of a chlorinated polyolefinic resin and an acrylic monomer with an isocyanate compound.
c. In Japanese Patent Laid-open Publication Number 62-18434, a resin combining a copolymer of a chlorinated polyolefinic resin, an acrylic monomer and a chlorinated polydiene with an isocyanate compound.